docs: def _report_completion(self):
          """Update shared counters to signal that we are done with this cluster.
          Call just before exiting run() method (in a finally clause)"""
          rem_clust = self.remaining_clusters
          if rem_clust is not None:
              # -= is non-atomic, need to acquire a lock
              with self.remaining_clusters_lock:
                  rem_clust.value -= 1
              # we do not need this object anymore
              self.remaining_clusters = None
              print("{} reported completion".format(self.name), file=self.log_fh)